I have a 1986 F150 with a 5.0 302. The truck is running fine but I have had continuous issues with oil leaks and severe blowby. I hear that this is common with many 302's but I was looking to try to at least reduce the problem as much as possible. I know that changing my piston rings will probably fix the blowby issue, but I'm looking for any cheaper solutions because I don't have the know how or money to tackle something like that. Any suggestions would be greatly appreciated

 

You may have a plugged PCV valve or system. The valve is plugged into a valve cover, usually at the rear of the passenger-side cover, and has a hose running to the carb or intake manifold. Pull the valve out of the cover with the engine running and there should be a strong vacuum on the bottom of it - strong enough to hold your finger to it tightly. If not, the valve may be stuck or plugged. You can pull it off and replace it cheaply, and with it off there should be a very strong vacuum on the hose.

Similarly, there should be a hose from the oil filler cap on the other valve cover going up to the air cleaner. It is to allow filtered air into the crankcase and then drawn out with all vapors into the carb via the valve. If the PCV system is plugged the blow-by will pressurize the crankcase and you will have oil leaks galore.

 

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Smart man!!

 

I have already replaced the pcv and it has not fixed the blowby or oil leaks

 

Well, how many miles are on this engine? and what part of the world do you live in? you could always use a thicker oil. That won't help the oil leaks a whole lot but it will help the blow by some.

 

Seen and fixed problems like yours many times and yes PCV is the answer but not just fixing it, you have to modify it. The stock PCV system will not flow enough. The stock type PCV valve is very restricting. Take it out and cut the bottom off it. A couple things will fall out and then it will just be a hose adapter. Then just plug it back in.

This may effect your idle but shouldn't on your stock EFI system if it's working right. But it will do a lot to fix the oil leaks and smoke caused by blow by.

If you want to go a step further do it on the other side also. The other side is a vent, instead of venting make it a second PCV. I did this on my 460 and went from using a quart of oil every 20 highway miles to using no oil.

Edit, I should add though that if the modification causes too much of a "vacuum leak" then either plug the other side or do the mod there to. The "vacuum leak" then can't pull any more volume of gasses then the engine blows by or seals leak slowing the "vacuum leak"

 

I disagree with your fix recommendation. A PVC is a "calibrated" vacuum leak. You do not want to remove the restriction. If you do, you will create a massive vacuum leak. I doubt your engine will compensate for the extreme lean condition you will create. Also if you add a PCV to "the other side" (which is the clean air inlet for the PVC) you will have no way to get fresh air into the crankcase to replace that air pulled out by the PVC. You end up pulling a vacuum on the crankcase which sucks oil into the engine and will cause engine seals to leak.
Higher viscosity oil is oaky. But leave the PVC system alone (make sure it works as intended) then fix the "real cause" of your blowby when you can.

 

Disagree all you want your disagreement doesn't effect the real world one little bit. The point stands that the "calibration" is no longer right for his engine. Why in the world would you want or need fresh air in your crankcase? And YES having vacuum in the crankcase is the whole point of the POSITIVE CRANKCASE VACUUM system.

It's only becomes a "massive vacuum leak" if the engine then lets in too much fresh air. After the mod the crankcase should maintain a vacuum much like the intake manifold. This helps seal seals, stop leaks, slows burning oil, and helps seal rings

 

That's not the point of the original design of the system. If it works for you and your engine, then that's great. But the original design did allow clean fresh air to enter the engine to replace the dirty air that the PCV system was sucking out.

He said he put a new PCV valve in, but didn't say if he had any suction on it when the engine was running. The hose can get clogged that hooks to the PCV valve.

If everything is working and you still have a lot of blowby(what are your symptoms, how do you know it has a lot of blowby?) your engine is wore out. You should see other signs of this, it has a lot of miles on it, has a few little knocking noises on cold start-up, etc. Putting new rings in it probably won't help either, it probably is going to need to be bored and oversize pistons installed. In other words a total rebuild. It's not uncommon, engines do wear out. These trucks are getting pretty old.

 

I don't really want a PCV argument but I'll just say that the original design is severely lacking. We change the original design on our trucks all the time where it's lacking, this should be one of them. There is NO reason to bring fresh air into your crankcase and every reason to keep it out. And there is no reason to limit the amount of vacuum in the crankcase and every reason to boost it.

 

We won't get into an argument - but we can share experiences, ideas and concepts. In my (mechanic's) training I learned that, the fresh air needs to get into the crankcase to keep the vacuum in the crankcase close to zero (you don't want a vacuum in the crankcase you just want to move the oil/fuel vapors out of the crankcase and pull back into engine to burn). If you create a vacuum in the crankcase the vacuum will pull air from "somewhere" and that means past the crank seals and/or valve covers, and/or manifold valley seals (where ever the weakest seal is) and you end up with an oil leak.